Hi, On Mon, Mar 18, 2013 at 10:44 PM, Alan Modra <amo...@gmail.com> wrote: > On Mon, Mar 18, 2013 at 06:18:58PM +0100, Richard Biener wrote: >> I was asking for the ifunc selector to be >> Overridable by ld_preload or a similar mechanism at dynamic load time. > > Please don't. Calling an ifunc resolver function in another library > is just asking for trouble with current glibc. Why? Well, the other > library containing the resolver function may not have had any dynamic > relocations applied. So if the resolver makes use of the GOT (to read > some variable), it will use unrelocated addresses. You'll segfault if > you're lucky.
Does this also mean that Paul's idea of doing: LD_CPU_FEATURES=sse,sse2 ./a.out # run as if only sse and sse2 are available is fraught with risk when used with IFUNC, particularly on x86_64? Shouldn't the IFUNC resolver go through the GOT even in this case. This could work well for the MV testing problem I explained earlier, but if this is not feasible with IFUNC in play I would like my original proposal reconsidered. Thanks Sri > > For anyone playing with ifunc, please test out your great ideas on > i386, ppc32, mips, arm, etc. *NOT* x86_64 or powerpc64 which both > avoid the GOT in many cases. > > -- > Alan Modra > Australia Development Lab, IBM
